Saint-Mleux Benoît, Bayer Laurence, Eggermann Emmanuel, Jones Barbara E, Mühlethaler Michel, Serafin Mauro
Département de Neurosciences Fondamentales, Centre Médical Universitaire, 1211 Genève 4, Switzerland.
J Neurosci. 2007 Jun 13;27(24):6412-6. doi: 10.1523/JNEUROSCI.1432-07.2007.
As the major brain circadian pacemaker, the suprachiasmatic nucleus (SCN) is known to influence the timing of sleep and waking. We thus investigated here the effect of SCN stimulation on neurons of the ventrolateral preoptic nucleus (VLPO) thought to be involved in promoting sleep. Using an acute in vitro preparation of the rat anterior hypothalamus/preoptic area, we found that whereas single-pulse stimulations of the SCN evoked standard fast ionotropic IPSPs and EPSPs, train stimulations unexpectedly evoked a long-lasting inhibition (LLI). Such LLIs could also be evoked in VLPO neurons by pressure application of NMDA within the SCN, indicating the specific activation of SCN neurons. This LLI was shown to result from the presynaptic facilitation of noradrenaline release, because it was suppressed in presence of yohimbine, a selective antagonist of alpha2-adrenoreceptors. The LLI depended on the opening of a potassium conductance, because it was annulled at E(K) and could be reversed below E(K). These results show that the SCN can provide an LLI of the sleep-promoting VLPO neurons that could play a role in the circadian organization of the sleep-waking cycle.
作为大脑主要的昼夜节律起搏器，视交叉上核（SCN）已知会影响睡眠和觉醒的时间。因此，我们在此研究了SCN刺激对被认为参与促进睡眠的腹外侧视前核（VLPO）神经元的影响。利用大鼠下丘脑前部/视前区的急性体外制备，我们发现，虽然对SCN的单脉冲刺激会诱发标准的快速离子型抑制性突触后电位（IPSPs）和兴奋性突触后电位（EPSPs），但串刺激意外地诱发了一种长效抑制（LLI）。通过在SCN内压力施加N-甲基-D-天冬氨酸（NMDA），VLPO神经元中也可诱发这种LLI，这表明SCN神经元的特异性激活。这种LLI被证明是由去甲肾上腺素释放的突触前易化导致的，因为在α2肾上腺素能受体的选择性拮抗剂育亨宾存在的情况下，它受到了抑制。LLI依赖于钾离子电导的开放，因为它在E(K)时被消除，并且在E(K)以下可以被逆转。这些结果表明，SCN可以对促进睡眠的VLPO神经元提供长效抑制，这可能在睡眠-觉醒周期的昼夜节律组织中发挥作用。
